The present research project is proposed in order to study the organization and developmental physiology of cat superior colliculus (SC) cells with regard to retinotectal, corticotectal and intertectal systems. Three related lines of research will be pursued: 1. Developmental studies will document the ontogeny of response and receptive field characteristics of SC cells with special attention given to the maturation of retinotectal and corticotectal systems. Electrophysiological recordings from single cells will be made in the SC and visual cortex, and neuronal responses to visual stimuli and to electrical stimulation of optic pathways will be studied from early postnatal stages to adulthood. We will attempt to relate the development of specific subpopulations of afferents to th progressive changes in response and receptive field characteristics of SC cells. 2. Behavioral-electrophysiological relationships will also be examined in kittens and adults after (a) extensive occipital-temporal lobectomy, and (b) subsequent intertectal section or contralateral SC removal. Behaviorally, (a) results in an animal resembling the colliculectomized reparation by ignoring contralateral visual stimuli. However, after (b), visually-guided behavior is reinstated. The electrophysiological changes which accompany the behavioral changes will be studied in order to learn which SC properties are essential for visually-guided behavior. 3. The growth of ipsilateral afferents will be encouraged by removal of one eye alone or in combination with the ipsilateral SC in the neonate. By initiating the "new" SC organization, it is hoped that we can facilitate efforts to understand how specific anatomical and electrophysiological properties of the SC relate to behavior.